Currently, radio receivers provide FM radio service continuity by virtue of the features of a radio data system, known by those skilled in the art by the acronym RDS, in which unique program identification (PI) codes are assigned to each radio station.
With these PI codes decoded, the radio receivers are capable of identifying whether an alternative frequency carries the same radio station as that currently being listened to and possibly performing a switchover to the alternative frequency in order to allow a station to be listened to without interruption when travelling.
However, the RDS service is not always available in all countries. For example, this RDS service is not deployed in China.
Moreover, some radio stations do not always provide the RDS service.
Also, since the sensitivity necessary to be able to decode the RDS information is not as good as that of the FM audio signals, a better reception quality is necessary to decode the PI codes.